Palm oil is an important global commodity. Palm oil is derived from oil palms, Elaeis. Elaeis are two species of the Arecacae, or palm family. The African oil palm Elaeis guineensis is native to West Africa, occurring between Angola and Gambia, while the American oil palm Elaeis oleifera is native to tropical Central America and South America. Elaeis, herein, is used to refer to any oil palm and Elaeis and palm are used interchangeably.
Three edible oils are derived from Elaeis. The three oils come from different parts of the plant. Coconut oil is extracted from the kernel of the coconut, palm oil is extracted from the pulp of Elaeis fruit and palm kernel oil is extracted from the kernel of Elaeis fruit. Palm oil as used herein will generally refer to the oil extracted from the pulp of Elaeis fruit.
Elaeis produces fruit within a fruit bunch. Each Elaeis tree produces approximately one fruit bunch per month for about 25 years. This ensures a constant and stable supply as compared with other annual crops. Each fruit bunch weighs from about 10 to 40 kilograms. The fruit bunch consists of fruit embedded in spikelets growing on a main stem. A single bunch contains multiple spikelets which cumulatively may contain as many as 3000 fruits. The individual fruit is reddish in color and about the size of a large plum, ranging in weight from 6 to 20 grams. The Elaeis fruit is made up of an outer skin (exocarp), a pulp (mesocarp) containing the palm oil in a fibrous matrix; a central nut consisting of a shell (endocarp); and the kernel, which itself contains oil having a different composition than the palm oil. The mesocarp comprises about 70-80% by weight of the fruit and about 45-50% of the mesocarp is oil. For every 100 kilograms of fruit bunches, typically 22 kilograms of palm oil and 1.6 kilograms of palm kernel oil can be extracted. The high oil yield from Elaeis, as high as 7,250 liters per hectare per year, makes it an effective source of oil.
The oil from Elaeis fruit is edible and has no known toxins. Palm oil is comprised of mainly triglycerides. Palmitic acid is the most abundant of the glycerides found in palm oil. Palmitic acid is a saturated fatty acid and hence palm oil is a viscous semi-solid, even at tropical ambient temperatures, and a solid fat in more temperate climates. Palm oil also contains minor components that are organically soluble, but not classified as oils. These include carotineoids, tocopherols, sterols, polar lipids and other fat-soluble impurities. The deep red color of palm oil is from the carotineoids in the palm oil.
Palm oil can be used in most food applications without hydrogenation. This reduces production cost by as much as 30% compared to other unsaturated oils. Palm oil is available in a variety of forms: crude palm oil, palm olein, palm stearin, refined bleached and deodorized palm oil, fractionated palm olein and palm mid-fraction. A range of products are available to suit a variety of manufacturing needs and in forms that are ready to use and require no further processing. These oil-based products are useful for cooking oil, food additives, feedstock additives, cosmetics, lubricants, fuel and soaps. In addition, the pulp and fibers from the processing of the fruit and bunches may be used as fodder (feedstock) for animals, fertilizer or as fuel.
Elaeis fruit must be processed in order to isolate and purify the oil within the mesocarp. The aim of processing palm oil is therefore to convert the crude oil to quality edible oil by reducing objectionable impurities to acceptable levels. Therefore, some compounds in the crude palm oil need to be removed or substantially reduced.
Palm oil mills are traditionally located near rivers from which water is taken for use in their processing operations. A number of palm oil mills conveniently discharge their POME into rivers, untreated. POME is a non-toxic, brownish, colloidal slurry of water, palm juice, oil and fine cellulosic fruit residue. POME contains appreciable amounts of N, P, K, Mg and Ca. POME also contains dissolved fatty acids, beta-carotenes and other nutritive components both fat soluble and water soluble. POME coming from the clarification process is usually at a temperature of between 80° C. and 90° C. and has a pH of from about 4 to about 5. POME has a very high biochemical oxygen demand and chemical oxygen demand, both of which are 100 times more than the oxygen demand from domestic sewage. This demand can create an environmental disaster in the waterways that the POME is discharged into.
The palm oil present in the effluent may float to the surface of the water body and form a wide-spread film which can prevent atmospheric oxygen from dissolving into its waters. Furthermore, when the organic load far exceeds its waste assimilation capacity, the available oxygen in the water body is rapidly consumed as a result of the natural biochemical processes that take place to break down the POME. The oxygen demand to break down the POME is so high that the water body may become completely devoid of dissolved oxygen. When this happens, anaerobic conditions are created in which hydrogen sulphide and other gases are generated and released into the environment resulting in objectionable odors. This riparian anaerobic condition will result in the decline and eventual destruction of aquatic life and the aquatic ecosystem.
If a convenient waterway is not available, POME is usually drained off into nearby evaporation pits and no further treatment of the POME is undertaken in most mills. The same anaerobic conditions form in these pits. The pits are eyesores and generate foul smelling gasses.
There are a few remediation techniques that are used to treat POME. One such remediation technique of POME involves anaerobic fermentation followed by aerobic fermentation in large ponds until the effluent quality is suitable for discharge. In some of the mills the treated effluent is used on the farm as manure and as a source of water for irrigation. The sludge accumulating in the fermentation ponds is periodically removed and fed to the land. In order to reduce the amount of POME, some mills employ expensive techniques such as de-watering and decanting centrifuges at various locations in the process line. These remediation techniques take a long time to finish and require additional human, industrial, economic and land resources. Therefore, the remediation techniques for POME are often not implemented at the palm oil mills.
POME is either disposed of at the expense of the environment or at the expense of the mills. Furthermore, valuable nutrients and oil are being discarded and put to no beneficial use. POME is a major environmental problem in Elaeis growing regions of the world. Valuable economic commodities are being thrown away.
Thus, there is a need in the palm oil processing industry to be able to reduce the amount of POME and to capture, and put to economic use, the nutrients and oil contained within POME and palm juice.